Animation artists create graphical object animations, such as cartoons and cartoon-like animations utilizing computing devices with various animation authoring tools and applications. Generally, animations are created as graphical objects that change over time, such as an animated object that appears to move across a display screen of a user device. The changes of a graphical object over time may be viewed as within the physical constraints that one would expect to see for a particular object, or the changes may be physical effects that are not physically realizable, but yet can be animated. For example, a cartoon character may stretch beyond what one would expect a person being physically capable of doing. In other instances, a graphical object may be animated over a time duration to change any number of properties, such as size, shape by morphing into a different shape, color, transparency, position, skew, rotation, and any other various properties of the object.
Physical simulation techniques are a traditional way to introduce natural and secondary effects in animations utilizing a computing device, but are exceedingly challenging to control. Further, creating physical-based simulations become more difficult as animators naturally want to add physical effects to animations that are not physically realizable. Inherently, physical simulation techniques attempt to maintain the animation of a graphical object within a realizable physical realm, while in contrast, an animator may want the graphical object animated beyond physical reality.
Keyframing techniques enables an animator to set all of the character poses of an animation object, and maintain tight control of key events and the animation shapes in select keyframes of an animation sequence. However, a natural, physical-based flow in the animation frames between each of the keyframes is often challenging or impossible to manually develop. Example-based techniques extend the standard physical simulation methods to bias simulated shapes towards artist created poses but cannot control when these poses are reached. Space-time optimization methods seek to find physical conditions that will satisfy the goals of an animator when developing an animation. However, these methods are computationally expensive, and remain challenging for an animator to direct and edit because key events are generally not realizable from optimized models. Constraint-based dynamics extend the physical simulation methods by constraining simulated materials to follow animator inputs, but still cannot produce exaggerations beyond the limits of the physical models.